Despite those scary outlooks, so far the tropical storm numbers are below average. But forecasters expect a comeback.
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What explains the lull in hurricane activity
Upper-air winds over western Africa that drive weather disturbances that can enter the Atlantic and eventually mature into hurricanes have been farther north than usual, said Rosencrans. That means the systems “can come off of Africa closer to dry Saharan air, and over waters not warm enough to sustain tropical storm development.”
Klotzbach said low pressure over west-central Africa has drawn drying winds from the north to the areas where hurricanes form. Winds circulate counterclockwise around low centers, and areas to the west of the center — in this case, the Atlantic — experience north winds.
In addition, he said that while the North Atlantic is warm, so is the upper atmosphere. Storms form when warmer air rises over cooler layers of air and condenses. If temperatures higher up are warmer, the air can’t rise.
Rosencrans said cloud-suppressing high pressure, or heavier air, over the North Atlantic has been putting a cap on thunderstorm activity. "
Entretanto, as "tropical waves" lá vão saindo, prometendo... e morrendo.
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Yet, after the dissipation of Ernesto, the Atlantic basin, which includes the Gulf of Mexico and the Caribbean Sea, went dead quiet. Some signs of awakening are evident, with the hurricane center giving two seedlings outside chances of becoming tropical systems later in the week, but Labor Day weekend proceeded without a tropical storm scare anywhere from the Texas to Florida to Maine coasts.
This would mark
the first time in 27 years that not a single named storm, those with winds of at least 39 mph, has developed in the Atlantic between Aug. 21 and Sept. 2, said Klotzbach.